Mr Summerskill wrote in a Stonewall eBulletin: “We hear via the lovely Amy Lamé on Twitter that lots of people are planning to give their religion as ‘lesbian’ in this month’s census, protesting at the absence of a question on sexual orientation.

“The census is designed to ‘help allocate public spending fairly’ and gay people contribute more than £40 billion a year to the cost public services. Our deliberate exclusion by the civil servants responsible is gratuitously offensive.”

The online campaign calls on everyone – including men and straight people – to say they are lesbian to “send a message” to census organisers when they fill out the forms on Sunday. A Facebook page currently has 126 members.

But gay writer and former barrister Brent Martin criticised the idea as “fundamentally misguided”.

He argued that it would distort census figures on religion and questioned whether LGBT people have “exclusive needs”.

“The thinking behind it is rather lazy because it assumes that we are a homogeneous group with the same or relatively similar needs that a census can identify,” Mr Martin wrote for the Guardian.

“This is, of course, utter rubbish. Overall, we are as diverse as the rest of society.”

The British Humanist Association has also called on people to avoid listing themselves as religious out of habit if they are not.

In 2009, the Equality and Human Rights Commission asked government ministers to include a question in the 2011 census on sexual orientation but the idea was ruled out.